Blade drive device and optical instrument

ABSTRACT

A blade drive device includes: a board including an opening; first and second blades opening and closing the opening; and first and second actuators respectively driving the first and second blades, wherein the first and second actuators respectively include first and second stators, first and second rotors, and first and second coils, and respectively drive the first and second blades through first and second drive members, the first drive member is arranged to overlap the first stator and the first coil in an optical axis direction, and the second drive member is arranged to overlap the second stator and the second coil in the optical axis direction.

CROSS-REFERENCE TO RELATED APPLICATION

This application is a continuation of and claims priority toInternational Patent Application No. PCT/JP2013/072450 filed on Aug. 22,2013, which claims priority to Japanese Patent Application No.2012-210079 filed on Sep. 24, 2012 and Japanese Patent Application No.2013-111175 filed on May 27, 2013, subject matter of these patentdocuments is incorporated by reference herein in its entirety.

BACKGROUND

(i) Technical Field

The present invention relates to blade drive devices and opticalinstruments.

(ii) Related Art

Japanese Unexamined Patent Application Publication No. 2009-175365discloses a blade drive device in which an actuator drives a blade toopen and close an opening in a board. The actuator is connected with adrive lever for driving the blade. The actuator and the drive lever aresupported on the board.

The positional relationship between the actuator and the drive levermight increase the space on the board occupied by these members. Thismight increase the size of the board in the planar directionperpendicular to an optical axis direction, so that the size of theblade drive device itself might be increased.

SUMMARY

It is thus object of the present invention to provide a blade drivedevice having a reduced size in a planar direction perpendicular to anoptical axis direction and an optical instrument having the same.

According to an aspect of the present invention, there is provided ablade drive device including: a board including an opening; first andsecond blades opening and closing the opening; and first and secondactuators respectively driving the first and second blades, wherein thefirst and second actuators respectively include first and secondstators, first and second rotors, and first and second coils, andrespectively drive the first and second blades through first and seconddrive members, the first drive member is arranged to overlap the firststator and the first coil in an optical axis direction, and the seconddrive member is arranged to overlap the second stator and the secondcoil in the optical axis direction.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is an exploded perspective view of a blade drive device accordingto the present embodiment;

FIG. 2 is an exploded perspective view of the blade drive deviceaccording to the present embodiment;

FIG. 3 is an enlarged view of a rotor, a drive member, and an outputmember;

FIG. 4 is a sectional view around a leading blade, the drive member, theoutput member, and an actuator;

FIGS. 5A and 5B are explanatory views of load applied to the drivemember;

FIG. 6 is a perspective view of the drive member, the output member, andthe rotor when viewed in an axial direction of an opening;

FIG. 7 is a sectional view of a blade drive device according to avariation;

FIG. 8 is a front view of the blade drive device;

FIG. 9 is an explanatory view of a unit;

FIGS. 10A and 10B are front views of blade drive devices according tovariations, and

FIG. 11 is a front view of a blade drive device according to avariation.

DETAILED DESCRIPTION

FIGS. 1 and 2 are exploded perspective views of a blade drive device 1according to the present embodiment. The blade drive device 1 is alsoreferred to as a focal plane shutter. The blade drive device 1 isemployed in an optical instrument such as a digital camera or a stillcamera. The blade drive device 1 includes boards 10, 10A, and 10B, aleading blade 20A, a trailing blade 20B, arms 31 a, 32 a, 31 b, and 32b, and actuators 70 a and 70 b. The boards 10, 10A, and 10B respectivelyinclude openings 11, 11A, and 11B. The leading blade 20A and thetrailing blade 20B open and close these openings 11, 11A, and 11B. Theactuators 70A and 70B drive the leading blade 20A and the trailing blade20B, respectively.

The leading blade 20A and the trailing blade 20B each includes pluralblades. Each of the leading blade 20A and the trailing blade 20B canshift between an overlapped state where the plural blades overlap oneanother and an expanded state where the plural blades are expanded.These plural blades in the overlapped state recede from the opening 11to cause the opening 11 to be in a fully opened state. These pluralblades in the expanded state close the opening 11 to cause the opening11 to be in a fully closed state. FIGS. 1 and 2 illustrate the bladedrive device 1 in the fully opened state.

The leading blade 20A is connected with the arms 31 a and 32 a. Thetrailing blade 20B is connected with the arms 31 b and 32 b. Asillustrated in FIG. 2, the arms 31 a, 32 a, 31 b, and 32 b are rotatablysupported by spindles 14 a, 15 a, 14 b, and 15 b provided in the board10, respectively.

Drive members 40 a and 40 b drive the arms 31 a and 31 b, respectively.Thus, the arms 31 a and 31 b correspond to driven members that aredriven by the drive members 40 a and 40 b and that drive the leadingblade 20A and the trailing blade 20B, respectively. The drive members 40a and 40 b are provided with drive pins 43 a and 13 b connected with thearms 31 a and 31 b, respectively. The boards 10, 10A, and 10B arerespectively formed with escape slots 13 a, 13 aA, and 13 aB forpermit-ting the movement of the drive pin 43 a. Likewise, they arerespectively formed with escape slots 13 b, 13 bA, and 13 bB forpermitting the movement of the drive pin 43 b. The drive members 40 aand 40 b will be described later in detail.

The board 10 is assembled with holders 80 and 90 holding the actuators70 a and 70 b. The holder 80 is formed. with support walls 81 a and 81 bthat respectively support the actuators 70 a and 70 b. The holder 80 issecured on the hoard 10. The holders 80 and 90 are secured to eachother. The holder 90 is provided with plural engaging claws 98. Theholder 80 is provided with plural engaging portions 88 which arerespectively engaged with the engaging claws 98. The holders 30 and 90are secured to each other by engaging the engaging claws 98 with theengaging portions 88. The holders 80 and 90 are made of a syntheticresin.

The actuator 70 a includes: a rotor 72 a rotatably supported by theholder 80; a stator 74 a excited to generate magnetic force between thestator and the rotor 72 a; and a leading blade coil 76 a for excitingthe stator 74 a. The rotor 72 a is fitted with an output member 50 a aswill be described later in detail. The output member 50 a is connectedwith the drive member 40 a. Therefore, the rotation of the rotor 72 adrives the output member 50 a and the drive member 40 a to drive thearm. 31 a and the leading blade 20A. The actuator 70 b has the samearrangement, The rotation of a rotor 72 b of the actuator 70 b drivesthe drive member 40 b to drive the trailing blade 20B.

The support walls 81 a and 81 b of the holder 80 are respectively formedwith escape holes 85 a and 85 b. The escape hole 85 a receives aconnection portion where the drive member 40 a and the output member 50a are connected with each other. Likewise, the escape hole 85 b receivesa connection portion where the drive member 40 b and an output member 50b are connected with each other. The holder 80 is formed with spindleportions 87 a and 87 b for supporting the rotors 72 a and 72 b forrotation, respectively. A printed circuit. board 100 is secured on anupper portion of the holder 90. The printed circuit board 100 suppliesthe coils 76 a and 76 b with power.

FIG. 3 is an enlarged view of the rotor 72 a, the drive member 40 a, andthe output member 50 a. Additionally, FIG. 3 illustrates a state wherethe rotor 72 a, the drive member 40 a, and the output member 50 a areassembled into the blade drive device 1. The drive member 40 a includes:an arm portion 41 a having a plate shape; a support hole 42 a formed atone end of the arm portion 41 a and serving as a fulcrum of rotation;and the drive pin 43 a formed at the other end of the arm portion 41 aand extending in a predetermined direction. Also, a gear portion 45 a isformed on the upper portion of the arm portion 41 a. The rotor 72 aincludes a cylindrical portion 72 a 3, and a permanent magnet 72 a 1having a ring shape and fitted with the cylindrical portion 72 a 3. Thepermanent magnet 72 a 1 is energized to have different polarities in thecircumferential direction. The permanent magnet 72 a 1 is fitted withthe upper side of the cylindrical portion 72 a 3 and is not rotatedrelative thereto. The output member 50 a is fitted with the lower sideof the cylindrical portion 72 a 3 and is not rotated relative thereto.Thus, the output member 50 a rotates together with the rotor 72 a. Thepermanent magnet 72 a 1 and the cylindrical portion 72 a 3 areintegrally formed with each other.

The output member 50 a includes: a cylindrical portion 52 a having asubstantially cylindrical shape and fitted with the cylindrical portion72 a 3; a projection portion 54 a projecting from the cylindricalportion 52 a in the radially outward direction; and a gear portion 55 aformed at one end of the projection portion 54 a. The gear portion 55 aof the output member 50 a meshes with the gear portion 45 a of the drivemember 40 a. Thus, the force of the output member 50 a is transmitted tothe drive member 40 a. Therefore, the gear portion 45 a of the drivemember 40 a corresponds to a first connection portion connected with theoutput member 50 a.

FIG. 4 is a sectional view around the leading blade 20A, the drivemember 40 a, the output member 50 a, and the actuator 70 a.Additionally, FIG. 4 is the sectional view of the blade drive device 1viewed in the direction perpendicular to the axial direction of theopening 11. The board 10A is omitted in FIG. 4. The support hole 42 a ofthe drive member 40 a is rotatably fitted onto a spindle 84 a of theholder 80. Accordingly, the drive member 40 a is rotatably supported.Thus, the support hole 42 a corresponds to a support portion thatrotatably supports the drive member 40 a. The drive pin 43 a extends ina predetermined direction and is connected with the arm 31 a arrangedbetween the boards 10 and 10B. Thus, the drive pin 43 a of the drivemember 40 a corresponds to a second connection portion connected withthe arm 31 a. As mentioned above, the arm 31 a is connected with theleading blade 20A. The connection between the output member 50 a and thedrive member 40 a is ensured through the escape hole 85 a. Specifically,the gear portions 45 a and 55 a are positioned in the escape hole 85 a.

Also, as illustrated in FIGS. 3 and 4, the gear portion 45 a of thedrive member 40 a is positioned between the support hole 42 a and thedrive pin 43 a. Therefore, the load applied to the spindle 84 a fittedinto the support hole 42 a can be reduced, thereby making the diameterof the spindle 84 a smaller than conventional one. A followingdescription will be given of the load exerted on the drive member 40 a.

FIGS. 5A and 5B are explanatory views of the load exerted on the drivemember 40 a. FIG. 5A is the explanatory view of the load exerted on thedrive member 40 a in the present embodiment, and FIG. 5B is theexplanatory view of the load exerted on a drive member having astructure different from the present embodiment. In the presentembodiment, the arm portion 41 a of the drive member 40 a is formed withthe drive pin 43 a fitted into the arm 31 a, and the support hole 42 afitted with the spindle 84 a. Thus, the arm portion 41 a of the drivemember 40 a can be considered as a both-end-supported beam B that issupported at points A2 and A3, as illustrated in FIG. 5A. The point A3corresponds to the support hole 42 a. The point A2 corresponds to thesecond connection portion where the arm 31 a is connected with the drivemember 40 a. Herein, it can be considered that the gear portion 45 aformed on the arm portion 41 a to which the force is transmitted fromthe output member 50 a is a load P exerted on the beam B. The length ofthe beam B is represented by 21. A point A1 where the load P is exertedis considered as the center of the beam B. The point A1 corresponds tothe first connection portion where the drive member 40 a and the outputmember 50 a are connected with each other. In this case, the magnitudeof the shear stress in the point A3 is P/2. The magnitude of the bendingmoment in the point A3 is zero.

In contrast, in FIG. 5B, the point A1 where the load is exerted ispositioned outside the point A3, and the point A3 is positioned betweenthe points A1 and A2. That is, FIG. 5B illustrates a conventionalstructure where the support hole 42 a of the present embodiment ispositioned between the gear portion 45 a and the drive pin 43 a of thedrive member 40 a. As mentioned above, the point A3 means the fulcrumwhere the drive member 40 a is rotatably supported. Therefore, a part ofthe beam B between the points A1 and A3 can be considered as acantilever beam that is supported at the point A3. The magnitude of theshear stress exerted on the point A3 is P. The magnitude of the bendingmoment exerted on the point A1 is PL. Thus, the shear stress and thebending moment exerted on the point A3 of the beam B illustrated in FIG.5A are smaller than those of the beam B illustrated in FIG. 5B,respectively.

Thus, in the present embodiment, the large load is not applied to thespindle 84 a that rotatably fits into the support hole 42 a of the drivemember 40 a. Accordingly, it is possible to make the diameter of thespindle 84 a smaller than that of the conventional structure where thesupport hole 42 a is arranged between the gear portion 45 a and thedrive pin 43 a. This reduces the size of the blade drive device 1 in theplanar direction.

Also, as illustrated in FIG. 4, the gear portion 45 a of the drivemember 40 a and the gear portion 55 a of the output member 50 a arepositioned in the escape hole 85 a of the holder 80. This reduces thethickness of the blade drive device 1.

Also, the size of the escape hole 85 a is set so as to permit theconnection between the gear portions 45 a and 55 a. Thus, the escapehole 85 a is comparatively large. This reduces the weight of the holder80.

Also, the gear portions 45 a and 55 a are connected with each other inthe escape hole 85 a, thereby arranging the drive member 40 a and theoutput member 50 a close to each other. This reduces the whole size ofthe drive member 40 a and the output member 50 a. Further, this reducesthe total weight of the drive member 40 a and the output member 50 a.Thus, the blade drive device 1 is reduced in weight.

FIG. 6 is a perspective view of the drive member 40 a, the output member50 a, and the rotor 72 a when viewed in the axial direction of theopening 11. In other words, FIG. 6 is the perspective view of the drivemember 40 a, the output member 50 a, and the rotor 72 a when viewed inthe axial direction of the rotor 72 a. As illustrated in FIG. 6, thedrive pin 43 a overlaps the rotor 72 a. Specifically, a part of atrajectory of the drive pin 43 a overlaps the rotor 72 a. The rotor 72 aand the drive member 40 a are arranged in such a manner, therebyreducing the size of the blade drive device 1 in the planar direction.Additionally, as illustrated in FIG. 6, the gear portion 45 a isarranged on a straight line that connects between the center of thesupport hole 42 a and the center of the drive pin 43 a.

FIG. 7 is a sectional view of a blade drive device 1′ according to avariation. FIG. 7 corresponds to FIG. 4. A drive member 40 a′ includes asupport spindle 42 a′. The support spindle 12 a′ is rotatably fittedwithin each hole formed in a holder 80′ and the board 10. Thus, thesupport spindle 42 a′ corresponds to a support portion that rotatablysupports the drive member 40 a. In such a manner, the drive member 40 a′may be rotated by the support spindle 42 a′. In such a configuration,the load exerted on the support spindle 42 a′ is small. It is thuspossible to make the size of the diameter of the support spindle 42 a′small, thereby reducing the size or the blade drive device 1′.

In the embodiment according to the present invention, the blade drivedevice 1 has been descried as the focal plane shutter. The focal planeshutter according to the present invention is not a type for usingsprings as drive sources of the leading blade 20A and the trailing blade20B, but a type for using the electromagnetic actuators 70 a and 70 b.In a general focal plane shutter, the space, in which a blade drivemechanism for driving the leading blade and the trailing blade can beconfigured, is limited to a region near one of the short sides of theopening 11 on the board 10 in the present embodiment, that is, a regiondefined by the holders 80 and 90 on the board 10.

In a case of the focal plane shutter equipped with the leading blade andthe trailing blade driven by the electromagnetic actuators 70 a and 70b, in order to ensure high speed in these days, the space might beneeded for a coil. Thus, the blade drive mechanism might be increased insize. In the focal plane shutter according to the present embodiment,the gear portion 45 a of the drive member 40 a is positioned between thesupport hole 42 a and the drive pin 43 a, and the large load is notapplied to the spindle 84 a. This can make the diameter of the spindle84 a small. Also, the trajectory of the drive pin 43 a partiallyoverlaps the rotor 72 a, thereby reducing the size of the blade drivemechanism in the planar direction. Further, the gear portion 45 a of thedriving member 40 a and the gear portion 55 a of the output member 50 aare arranged in the escape hole 85 a, whereby the thickness of the bladedrive mechanism can be reduced in thickness direction, that is, in thedirection of the spindle 84 a. Thus, in the focal plane shutter of theblade drive device 1 according to the present invention, the thicknessthereof is reduced in the optical axis direction parallel to the spindle84 a, and the size is reduced in the direction perpendicular to theoptical axis direction.

Next, the arrangements of the actuators 70 a and 70 b in the blade drivedevice 1 will be described. FIG. 8 is a front view of the blade drivedevice 1. Additionally, parts are omitted in FIG. 8. As illustrated inFIG. 8, the rotors 72 a and 72 b are arranged to sandwich the coils 76 aand 76 b. In other words, the rotors 72 a and 72 b are respectivelylocated at both ends of the holder 80 in the movable direction. of theleading blade 20A and the trailing blade 20B. In such a way, althoughthe actuators 70 a and 70 b are adjacent to each other, the rotors 72 aand 72 b are spaced apart from each other. This prevents the rotors 72 aand 72 b from magnetically influencing each other and from influencingthe driving properties of the rotors 72 a and 72 b. It is thereforepossible to ensure the desired driving properties of the leading blade20A and the trailing blade 20B. Herein, the leading blade 20A and thetrailing blade 20B are an example of first and second blades. Theactuators 70 a and 70 b are an example of first and second actuators.The rotors 72 a and 72 b are an example of first and second rotors. Thecoils 76 a and 76 b are an example of first and second coils.

For example, the exposure operation is performed as follows. In thestate where the leading blade 20A closes the opening 11 and the trailingblade 20B recedes from the opening 11 and the rotors 72 a and 72 b stop,the rotor 72 a starts rotating and the leading blade 20A moves away fromthe opening 11 to open the opening 11. After that, the rotor 72 b startsrotating and the trailing blade 20B closes the opening 11. In thismanner, the timing when the rotor 72 a starts rotating is different fromthe timing when the rotor 72 b starts rotating in the exposureoperation. Therefore, for example, there is a state where one of therotors 72 a and 72 b is rotating and the other stops. Thus, in a casewhere the two rotors 72 a and 72 b are adjacent to each other, therotation of one of the rotors 72 a and 72 b might change the magneticfield to influence the other of the rotors 72 a and 72 b. Specifically,the change in the magnetic field of the rotor 72 a that firstly startsrotating might cause variations in the timing when the rotor 72 b startsrotating. This might cause variations in the period from the time whenthe leading blade 20A starts opening the opening 11 to the time when thetrailing blade 20B fully closes the opening 11, that is, in the exposureperiod. However, in the present embodiment as mentioned above, therotors 72 a and 72 b are not adjacent to each other, whereby the drivingproperties of the rotors 72 a and 72 b are prevented from beinginfluenced.

Additionally, the actuators 70 a and 70 b are arranged such thelongitudinal directions thereof are the same as the movable direction ofthe leading blade 20A and the trailing blade 20B. Further, the actuators70 a and 70 b are arranged in the longitudinal direction. Furthermore,the rotors 72 a and 72 b are respectively arranged at both ends of thewhole region of the actuators 70 a and 70 b in its longitudinaldirection. It is therefore possible to further ensure the intervalbetween the rotors 72 a and 72 b. This prevents the rotors 72 a and 72 bfrom magnetically influencing each other and from influencing thedriving properties of the rotors 72 a and 72 b.

Also, FIG. 8 illustrates the rotational ranges of the drive members 40 aand 40 b. Herein, when the blade drive device 1 is viewed in thedirection of the optical axis passing through the opening 11, at leastpart of the drive member 40 a and at least part of the output member 50a overlap the stator 74 a or the coil 76 a. Likewise, at least part ofthe drive member 40 b and at least part of the output member 50 boverlap the stator 74 b or the coil 76 b. Therefore, the coils 76 a and76 b each having a large size can be employed. Likewise, the stators 74a and 74 b each having a large size can be employed. Accordingly, thetorque and the speed of the rotors 72 a and 72 b can be improved. Thus,the movement speed of the leading blade 20A and the trailing blade 20Bcan be improved, so the shutter speed can be improved. Additionally, atleast part of the drive member 40 a or at least part of the outputmember 50 a may protrudes from at least part of the stator 74 a and thecoil 76 a. Likewise, at least part of the drive member 40 b or at leastpart of the output member 50 b may protrudes from at least part of thestator 74 b and the coil 76 b. Herein, the output members 50 a and 50 bare an example of first and second output members. The drive members 40a and 40 b are an example of first and second drive members. The stators74 a and 74 b are an example of first and second stators.

Additionally, as illustrated in FIGS. 4, 7, and 8, when the blade drivedevices 1 and 1′ are viewed in the direction of the optical path passingthrough the opening 11, the rotational ranges of the drive members 40 aand 40 a′ are set not to overlap a region R beneath the spindle portion87 a. Likewise, the rotational range of the drive member 40 b is set notto overlap a region beneath the spindle portion 87 b. This can ensurethe thicknesses of portions of the holder 80 supporting roots of thespindle portions 87 a and 87 b that respectively support the rotors 72 aand 72 b for rotation. This makes it possible to ensure the rigidity ofthe root portions of the spindle portions 87 a and 87 b, therebysupporting the rotors 72 a and 72 b in a stable manner.

Further, the ratio of the gear portion 45 a to the gear portion 55 a isset such that the rotational speed of the drive member 40 a is greaterthan that of the output member 50 a. That is, the pitch diameter of thegear portion 45 a is larger than that of the gear portion 55 a.Likewise, the ratio of the gear portion 45 b to the gear portion 55 b isset such that the rotational speed of the drive member 40 b is greaterthan that of the output member 50 b. Therefore, the drive members 40 aand 40 b can be respectively rotated much faster than the rotors 72 aand 72 b, thereby improving the movement speed of the leading blade 20Aand the trailing blade 20B. This also improves the shutter speed.

Further, as mentioned above, the drive force of the actuator 70 a istransmitted to the leading blade 20A through the gear portions 45 a and55 a. There is backlash between the gear portions 45 a and 55 a in orderto facilitate the rotation thereof. That is, a certain clearance betweenthe gear portions 45 a and 55 a is ensured. The drive member 40 arotates and the drive pin 43 a abuts the end portion of the escape slot13 a and the like, so the leading blade 20A stops. When the leadingblade 20A stops, the impact is applied to the drive member 40 a. Thisimpact can be absorbed by the backlash provided between the gearportions 45 a and 55 a. It is therefore possible to reduce the load onthe drive member 40 a and the output member 50 a. It is also possible toprevent the bound of the drive member 40 a when the drive member 40 aabuts the end portion of the escape slot 13 a or the like. This preventsthe leading blade 20A receding from the opening 11 from moving towardthe opening 11 again due to the bound of the drive member 40 a. Thedrive member 40 b, the output member 50 b, and the trailing blade 20Bhave the same arrangement. Herein, the gear portions 55 a and 55 b arerespective examples of first and second output teeth portions. The gearportions 45 a and 45 b are respective examples of first and secondfollowing teeth portions.

Additionally, the output members 50 a and 50 b are integrally formedwith the rotors 72 a and 72 b, respectively. For example, laser weldingis used, but other welding or insert molding may be used. Further, therotor 72 a and the output member 50 a may be integrally made of a resinmixed with magnetic powder.

FIG. 9 is an explanatory view of a unit U. The unit U includes theholders 80 and 90, and the actuators 70 a and 70 b. In such a way, thetwo actuators 70 a and 70 b are attached to the holders 80 and 90 to beassembled into the single unit U, handled, and managed. In this manner,the unit U integrated with the holders 80 and 90 is attached to theboard 10 or the like, so the blade drive device 1 is accomplished. Thus,the unit U can be tested for operation before being attached to theboard 10 or the like. For example, in a case where the actuator 70 a orthe like is found defective in the operation test after the blade drivedevice 1 is accomplished, the defective actuator 70 a or the like has tobe replaced. Alternately, the blade drive device 1 equipped with normalparts has to be abolished. However, in the present embodiment, theactuators 70 a and 70 b are handled as the unit U, so the operation testof the unit U can be performed before being attached to the board 10. Itis therefore possible to prevent the influence on the driving propertiesof the rotors 72 a and 72 b, and it is possible to avoid replacingdefective parts and to avoid wasting normal parts. This suppresses anincrease in manufacturing cost.

FIG. 10A is an explanatory view of a blade drive device 1″ according toa variation. Additionally, similar components will be denoted by thesimilar reference numerals, and a detailed description of suchcomponents will be omitted. Further, parts are omitted in FIG. 10A. Asillustrated in FIG. 10A, actuators 70 a″ and 70 b″ are arranged awayfrom each other to sandwich the opening 11. Also in this case, therotational ranges of drive members 40 a″ and 40 b′ are set not tooverlap spindle portions 87 a″ and 87 b″. Thus, rotors 72 a″ and 72 b″can be supported in a stable manner.

FIG. 10B is an explanatory view of a blade drive device 1′″ according toa variation. Additionally, similar components will be denoted by thesimilar reference numerals, and a detailed description of suchcomponents will be omitted. Further, parts are omitted in FIG. 10B. Theblade drive device 1′″ is provided with a single actuator 70 b′″, butnot the leading blade 20A or the actuator 70 a. The blade drive device1′″ is mounted on a camera in which an electronic leading blade canartificially move. As sequentially resetting charges stored in an imagepickup element for every pixel line in a predetermined direction, theelectronic leading blade artificially moves. Also in this case, therotational range of a drive member 40 b′″ is set not to overlap aspindle portion 87 b′″, thereby supporting a rotor 72 b′″ in a stablemanner.

FIG. 11 is an explanatory view of a blade drive device 1 c according toa variation. Additionally, similar components will be denoted by thesimilar reference numerals, and a detailed description of suchcomponents will be omitted. Further, parts are omitted in FIG. 11.Adjacent actuators 70 ac and 70 bc are arranged to face the same side.In other words, only a coil 76 bc is arranged to be sandwiched betweenrotors 72 ac and 72 bc, the rotor 72 bc is arranged at the end of thewhole region of the actuators 70 ac and 70 bc, and the coil 76 ac isarranged at the other end thereof. Also in this case, the rotationalranges of drive members 40 ac and 40 bc are set not to overlap spindleportions 87 ac and 87 bc. Thus, rotors 72 ac and 72 bc can be supportedin a stable manner.

Further, even in the above case where the rotors 72 ac and 72 bc onlysandwich the coil 76 bc, the rotors 72 ac and 72 bc are prevented frommagnetically influencing each other and are prevented from influencingthe driving properties of the rotors 72 ac and 72 bc. Even in a casewhere the rotors 72 ac and 72 bc only sandwich the coil 76 ac, the sameeffect is achieved. That is, the rotors 72 ac and 72 bc that are anexample of first and second rotors have only to sandwich at least one ofthe coils 76 ac and 76 bc that are an example of first and second coils.

While the exemplary embodiments of the present invention have beenillustrated in detail, the present invention is not limited to theabove-mentioned embodiments, and other embodiments, variations andmodifications may be made without departing from the scope of thepresent invention.

Finally, several aspects of the present invention are summarized asfollows.

According to an aspect of the present invention, there is provided ablade drive device including: a board including an opening; first andsecond blades opening and closing the opening; and first and secondactuators respectively driving the first and second blades, wherein thefirst and second actuators respectively include first and secondstators, first and second rotors, and first and second coils, andrespectively drive the first and second blades through first and seconddrive members, the first drive member is arranged to overlap the firststator and the first coil in an optical axis direction, and the seconddrive member is arranged to overlap the second stator and the secondcoil in the optical axis direction.

Since the first drive member is arranged to overlap the first stator andthe first coil in an optical axis direction and the second drive memberis arranged to overlap the second stator and the second coil in theoptical axis direction, the blade drive device has a reduced size in aplanar direction perpendicular to the optical axis direction.

According to another aspect of the present invention, there is providedan optical instrument having the above blade drive device.

What is claimed is:
 1. A blade drive device comprising: a boardincluding an opening; first and second blades opening and closing theopening; and first and second actuators respectively driving the firstand second blades, wherein the first and second actuators respectivelyinclude first and second stators, first and second rotors, and first andsecond coils, and respectively drive the first and second blades throughfirst and second drive members, the first drive member is arranged tooverlap the first stator and the first coil in an optical axisdirection, the second drive member is arranged to overlap the secondstator and the second coil in the optical axis direction, and an axis ofthe first drive member overlaps the first stator and the first coil andis positionally displaced from an axis of the first rotor.
 2. The bladedrive device of claim 1, wherein an axis of the second drive memberoverlaps the second stator and the second coil and is positionallydisplaced from an axis of the second rotor.
 3. The blade drive device ofclaim 1, wherein the first rotor is arranged not to overlap the firstcoil in the optical axis direction, and the second rotor is arranged notto overlap the second coil in the optical axis direction.
 4. The bladedrive device of claim 1, wherein the first and second rotors arearranged to sandwich the first and second coils.
 5. The blade drivedevice of claim 1, wherein the first and second actuators are arrangedin a longitudinal direction of the first actuator and in a longitudinaldirection of the second actuator, and the first and second rotors arerespectively arranged at both end portions in the longitudinal directionof a whole region of the first and second actuators.
 6. The blade drivedevice of claim 1, further comprising a first output member rotatingtogether with the first rotor, wherein the first drive member is engagedwith the first output member and drives the first blade, and at leastpart of the first output member and at least part of the first drivemember overlap at least part of the first stator and the first coil inthe optical axis direction.
 7. The blade drive device of claim 6,wherein the first output member includes a first output teeth portion,and the first drive member includes a first following teeth portionmeshing with the first output teeth portion.
 8. The blade drive deviceof claim 6, wherein the first output member is integrally formed withthe first rotor.
 9. The blade drive device of claim 1, furthercomprising a holder holding both the first and second actuators andattached to the board, wherein the first and second actuators areunitized with the holder.
 10. An optical instrument comprising a bladedrive device comprising: a board including an opening; first and secondblades opening and closing the opening; and first and second actuatorsrespectively driving the first and second blades, wherein the first andsecond actuators respectively include first and second stators, firstand second rotors, and first and second coils, and respectively drivethe first and second blades through first and second drive members, thefirst drive member is arranged to overlap the first stator and the firstcoil in an optical axis direction, the second drive member is arrangedto overlap the second stator and the second coil in the optical axisdirection, and an axis of the first drive member overlaps the firststator and the first coil and is positionally displaced from an axis ofthe first rotor.